Synthesis, crystal structure, antibacterial activity and theoretical studies on a novel mononuclear cobalt(II) complex based on 2,4,6-tris(2-pyridyl)-1,3,5-triazine ligand

•A new Co(II) complex with formula [Co(tptz)(CH3OH)Cl2]·CH3OH·0.5H2O has been prepared.•Using tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine as ligand.•The antibacterial activity of Co(II), Ni(II), Cu(II), Mn(II) and Rh(III) with tptz have been evaluated.•The DFT studies consistent with experimental results.

A cobalt complex was prepared from CoCl2·6H2O and 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) in methanol and designated as [Co(tptz)(CH3OH)Cl2]·CH3OH·0.5H2O (1). It was characterized by several techniques including TGA analysis and FT-IR, UV–Vis and 1H NMR spectral studies. The crystal structure of 1 was determined by single-crystal X-ray diffraction. The Co(II) metal center in 1 is six coordinated with a distorted octahedral geometry. The tptz ligand is tridentate and coordinates to the cobalt through coplanar nitrogen atoms from the triazine and two pyridyl rings. Two chloride anions and a methanol molecule complete the inner coordination sphere of the metal ion. The optimized geometrical parameters obtained by DFT calculation are in good agreement with single XRD data. The in vitro antibacterial activity of various tptz complexes of Co(II), Ni(II), Cu(II), Mn(II) and Rh(III) were evaluated against Gram-positive (Bacillus subtilis, Staphylococcus aureus and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. Whereas all complexes exhibited good activity in comparison to standard antibacterial drugs, the inhibitory effects of complexes were found to be more than that of the parent ligand. Overall, the obtained results strongly suggest that the cobalt(II) complex is a suitable candidate for counteracting antibiotic resistant microorganisms.

Graphical abstractThe crystal structure of Co(II) with formula [Co(tptz)(CH3OH)Cl2]·CH3OH·0.5H2O, (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) was determined by single-crystal X-ray diffraction. The DFT studies consistent with experimental results. Then, the in vitro antibacterial activity of ligand and tptz complexes of Co(II), Ni(II), Cu(II), Mn(II) and Rh(III) have been evaluated.Figure optionsDownload full-size imageDownload as PowerPoint slide